Scala Json Utils

  implicit class JsPathMixin(path: JsPath) extends JsPath {
    def readOrError[T](fieldMissingError: => String)(implicit r: Reads[T]): Reads[T] = (json: JsValue) => {
      path.readNullable(r)
        .reads(json) match {
        case JsSuccess(Some(value), _) => JsSuccess(value, path)
        case JsSuccess(None, _) => JsError(path, JsonValidationError(fieldMissingError))
        case err@JsError(_) =>
          err
      }
    }

    def readOrError[T](fieldMissingError: => String,
        constraintValidationError: => String)(implicit r: Reads[T]): Reads[T] = (json: JsValue) => {
      path.readNullable(r)
        .reads(json) match {
        case JsSuccess(Some(value), _) => JsSuccess(value, path)
        case JsSuccess(None, _) => JsError(path, JsonValidationError(fieldMissingError))
        case err@JsError(_) =>
          JsError(path, JsonValidationError(constraintValidationError))
      }
    }
  }

  def formatValidationErrors(errors: Seq[(JsPath, Seq[JsonValidationError])]): JsObject = {
    errors.foldLeft(JsObject.empty) { (obj, error) =>
      obj ++ JsObject(Seq(error._1.toString.replaceFirst("/", "") -> error._2.foldLeft(JsArray.empty) { (arr, err) =>
        val msg = {
          err.messages.map(JsString).toArray[JsValue]
        }
        msg.foldLeft(arr) { (acc, err) => acc :+ err }
      }))
    }
  }